System For Selecting A Transmission Economy-Based Shift Schedule

ABSTRACT

The present invention provides a method of selecting an economy mode shift schedule for a transmission coupled to a motor vehicle. The method includes calculating vehicle acceleration and determining a change in accelerator pedal position. Also, a net tractive effort force of the vehicle is determined for a current gear range of the transmission. Also, the method includes comparing the net tractive effort force for the current gear range to a maximum tractive effort force for a desired gear range and selecting the economy mode shift schedule for the transmission based on the comparison. The method further includes controlling shifting between one or more gear ranges of the transmission according to the economy mode shift schedule.

RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 61/389,414, filed Oct. 4, 2010, which is hereby incorporated byreference in its entirety.

BACKGROUND

The present invention relates to a motor vehicle transmission having aplurality of automatically selectable gear ranges, and in particular, toa system of selecting an economy-based shift schedule for a transmissionin a vehicle.

Conventional vehicle transmissions include software or a control schemefor determining when the automatic transmission shifts from one gearrange (or ratio) to another gear range. This control scheme is commonlyreferred to as a “shift schedule” and is based on multiple factors,e.g., engine torque, vehicle speed, accelerator pedal position (i.e.,throttle percentage), transmission output speed, and tractive effort.Any given shift schedule for a vehicle balances fuel economy againstperformance, and so a shift schedule may be categorized as an “economyshift schedule” or a “performance shift schedule” based on the balancethat characterizes the shift schedule. For example, in an economy-biasedshift schedule, a transmission operates in an economy shift schedulemore often than it operates in a performance shift schedule.

Also, it is desirable to be able to change shift schedules duringvehicle operation since there are times when better fuel economy ispreferred over high-performance and vice-versa. For example, when thevehicle is heavily loaded or is ascending a steep grade, thetransmission may detect such a condition and select a performance-basedshift schedule. Alternatively, when the vehicle is able to quicklyaccelerate, e.g., when the vehicle is unloaded or descending a steepgrade, the transmission may detect this condition and select aneconomy-based shift schedule.

In a conventional vehicle having an engine and automatic transmission,an engine control module (ECM) controls the engine and a transmissioncontrol module (TCM) controls the transmission. A wiring harness isprovided that electrically connects the ECM to the TCM so thatinformation related to the engine can be communicated to the TCM.Transmission software is downloaded to the TCM and includes multipleshift schedules that control when the transmission shifts from one gearratio to another gear ratio. During vehicle operation, the TCM detects adriving condition or a change in a driving condition and selects a shiftschedule accordingly.

For the transmission to detect the driving condition or the change in adriving condition, the TCM receives engine data from the ECM andpossibly other information about the vehicle from other sources. Assuch, the transmission must be compatible with the engine and otheroutside sources to receive this information. For a transmission tooperate effectively with the engine, transmission manufacturers mustwork closely with engine manufacturers to ensure that the TCM timelyreceives engine data from the ECM. As a result, transmissions can onlybe mounted behind engines from which the TCM is able to receive enginedata.

If a transmission were mounted behind an engine with which it is notcompatible, the ECM might not be able to communicate engine data (e.g.,engine torque) to the TCM and the TCM might therefore be unable toselect the appropriate shift schedule. Alternatively, even if the ECMwere able to communicate engine data to the TCM, the ECM still might notbe able to communicate the correct data or might provide the data to theTCM too slowly. As a result, as driving conditions change, the TCM wouldbe unable to select a different shift schedule based on the changingdriving condition because it would be waiting to receive engine datafrom the ECM. These problems undesirably limit the number of vehicles inwhich a given transmission can be installed and require costly andtime-consuming coordination efforts between engine and transmissiondesign teams.

In addition, some transmissions can only operate in an economy mode orperformance mode based on the type of shift schedule being performed. Assuch, a transmission can be shifting between gear ranges according toshift points in a performance shift schedule and be unable to switch toan economy shift schedule under certain conditions. Alternatively, atransmission may be able to switch between shift schedules, but thevehicle productivity is negatively affected.

What is needed is an improved system of selecting a transmissioneconomy-based shift schedule when fuel economy can be improved andvehicle performance will not be negatively affected. Further, it wouldbe desirable to be able to select the economy-based shift schedulequickly and without regards to the shift schedule under which thetransmission is performing at the time of making the selection.

SUMMARY OF THE INVENTION

The present invention provides a method of selecting an economy modeshift schedule for a transmission coupled to a motor vehicle. Thetransmission has a transmission control circuit and the vehicle has anengine control circuit. The method includes calculating vehicleacceleration and determining a change in accelerator pedal position. Thenet tractive effort force of the vehicle is determined for a currentgear range of the transmission. Also, the net tractive effort force forthe current gear range is compared to a maximum tractive effort forcefor a desired gear range. The method further includes selecting theeconomy mode shift schedule for the transmission based on the comparisonand controlling shifting between one or more gear ranges of thetransmission according to the economy mode shift schedule.

In addition, the comparing step can include comparing the vehicleacceleration to a threshold. If the vehicle acceleration exceeds thethreshold, the selecting and controlling steps are not completed.Similarly, the comparing step can also include comparing the change inaccelerator pedal position to a threshold. If the change in acceleratorposition exceeds the threshold, the selecting and controlling steps arenot completed.

In one embodiment, if the net tractive effort force is less than thetotal of the maximum tractive effort force and a threshold, theselecting and controlling steps are completed. Further, if the nettractive effort force is less than the total of the maximum tractiveeffort force and the threshold, the transmission shifts from a lowergear range to a higher gear range. The method can further includedetermining if, after the transmission shifts from the lower gear rangeto the higher gear range, the transmission shifts from the higher gearrange to the lower gear range within a period of time. As such, thethreshold can be adjusted if the transmission shifts from the highergear range to the lower gear range within the period of time.

In a different embodiment, the step of determining the net tractiveeffort force can include receiving engine torque data over a data linkestablished between the transmission control circuit and the enginecontrol circuit such that the engine torque data corresponds to enginespeed and a maximum accelerator pedal position. This step can alsoinclude computing a ratio value of a rear axle and tire size of thevehicle, determining a state of a torque-generating mechanism of thetransmission, determining gear ratios for the one or more gear ranges ofthe transmission, and computing the net tractive effort force of thevehicle as a function of the engine torque data, the ratio value of therear axle and tire size of the vehicle, the state of thetorque-generating mechanism, and the gear ratios of the transmission.Vehicle speed and transmission output speed can be determined such thatthe computed ratio value is a function thereof Also, in the step ofdetermining a state of a torque-generating mechanism, a determination ismade whether a torque converter of the transmission is in a convertermode or lockup mode.

In another embodiment, a system is provided for selecting an economymode shift schedule for a motor vehicle. The system includes atransmission having a torque converter and a plurality of selectablegear ranges and a transmission control circuit including a controlmodule having the economy mode shift schedule stored therein. Thetransmission control circuit is configured to operably control thetransmission. The system also includes an engine control circuitconfigured to control operation of an engine. The engine is operablycoupled to the transmission. In addition, a communication link isconfigured to transfer information between the transmission controlcircuit and the engine control circuit. The control module furtherincludes instructions stored therein for executably controlling thetransmission control circuit to receive engine torque data from thecommunication link, calculate vehicle acceleration, determine anaccelerator pedal position, determine a mode of the torque converter,compute a net tractive effort force of the vehicle, compare the vehicleacceleration to a first threshold, the accelerator pedal to a secondthreshold, and the net tractive effort force to a third threshold,select the economy mode shift schedule for the transmission based on thecomparison, and control shifting between gear ranges of the transmissionaccording to the economy mode shift schedule.

In one form of this embodiment, the instructions stored in the controlmodule can include instructions that are executable by the transmissioncontrol circuit to determine the net tractive effort force as a functionof the engine torque data, the gear ratio of a selected gear range, andthe mode of the torque converter. In another form thereof, theinstructions stored in the control module can include instructionsexecutable by the transmission control circuit to compute a ratio valueof a rear axle and tire size of the vehicle and determine gear ratiosfor the selectable gear ranges of the transmission.

In the system, the instructions stored in the control module can includeinstructions executable by the transmission control circuit forcontrolling a shift from a first gear range to a second gear range. Theinstructions stored in the control module can further includeinstructions executable by the transmission control circuit to determineif, after the transmission shifts from the first gear range to thesecond gear range, the transmission shifts from the second gear range tothe first gear range within a period of time.

In an alternative embodiment of the system, the third threshold caninclude a maximum tractive effort force and a tractive effort thresholdvalue. In addition, the instructions stored in the control module canfurther include instructions executable by the transmission controlcircuit for adjusting the tractive effort threshold value.

In a different embodiment, a method of operating a motor vehicle at anoptimal vehicle speed without negatively affecting vehicle productivityis provided. The method includes determining gear ratios of all gearranges of the transmission, receiving engine torque data as a functionof engine speed for all gear ranges, and calculating vehicleacceleration and determining accelerator pedal position. In addition, anet tractive effort force of the vehicle is determined for a currentgear range of the transmission. The method also includes comparing thevehicle acceleration to a first threshold, the accelerator pedalposition to a second threshold, and the net tractive effort force to athird threshold. The method further includes selecting an economy modeshift schedule for the transmission based on the comparison andcontrolling shifting between one or more gear ranges of the transmissionaccording to the economy mode shift schedule.

In one form of this embodiment, the controlling shifting can includedetermining if an upshift from a lower gear range to a higher gear rangecan be completed. The method can also determine if, after the upshiftfrom a lower gear range to a higher gear range is completed, thetransmission downshifts from the higher range to the lower range withina period of time. Further, the method can include adjusting the thirdthreshold when the transmission downshifts from the higher range to thelower range within the period of time.

In another form of this embodiment, when the economy mode shift scheduleincludes at least a first gear range having a first gear ratio, a secondgear range having a second gear ratio, and a third gear range having athird gear ratio, the second gear ratio being less than the first gearratio and the third gear ratio being less than the second gear ratio,the controlling shifting can include shifting from the first gear rangeto the second gear range. In this embodiment, after shifting from thefirst gear range to the second gear range, the method is repeated. Also,the method can include shifting from the second gear range to the thirdgear range. Alternatively, the method can include shifting from thefirst gear range to the third gear range.

In an alternative embodiment, a method is provided for selecting aneconomy mode shift schedule for a transmission having X selectable gearranges and coupled to a powered vehicle. The transmission has atransmission control circuit and the vehicle has an engine controlcircuit for controlling an engine. The method includes calculatingvehicle acceleration and a change in accelerator pedal position;computing a net tractive effort force of the vehicle for a current gearrange N of the transmission, where N<X; determining a maximum tractiveeffort force for all upshift gear ranges, the upshift gear rangescomprising gear ranges N+1, N+2, . . . , and N+J, where J=X−N; comparingthe net tractive effort force to each maximum tractive effort force; andselecting the economy mode shift schedule for the transmission based onthe comparison.

In one aspect of this embodiment, the method includes controllingshifting between gear range N and one of the upshift gear ranges. Inanother aspect, the method can include (a) determining which of theupshift gear ranges has a maximum tractive effort force greater than thenet tractive effort force; (b) for those upshift gear ranges satisfyingthe condition of step (a), calculating the difference between themaximum tractive effort force of those upshift gear ranges and the nettractive effort force; and (c) identifying the upshift gear rangecorresponding to the smallest difference calculated in step (b). Thecontrolling step may comprise shifting from gear range N to the upshiftgear range identified in step (c).

In addition, the method can include determining if, after the shift fromgear range N to the upshift gear range, the transmission downshifts fromthe upshift gear range to gear range N within a period of time. Themaximum tractive effort force associated with the upshift gear range canbe adjusted when the transmission downshifts from the upshift gear rangeto gear range N within the period of time. The controlling step of themethod can include shifting from gear range N to upshift gear range L,where L is between N and M, and upshift gear range M corresponds to theupshift gear range identified in step (c). Further, the method caninclude adding a constant threshold value to each maximum tractiveeffort force.

An advantage of shifting to the economy shift schedule, as described inthe present disclosure, is improving the fuel efficiency of the vehiclecarrying the transmission. The economy shift schedule can be selectedregardless of the type of shift schedule the transmission previously wasoperating in. As such, the economy shift schedule can be selected evenwhen the vehicle operates according to a performance-based shiftschedule.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned aspects of the present invention and the manner ofobtaining them will become more apparent and the invention itself willbe better understood by reference to the following description of theembodiments of the invention, taken in conjunction with the accompanyingdrawings, wherein:

FIG. 1 is a perspective view of one embodiment of a transmission coupledto a controller via a wiring harness; and

FIG. 2 is a diagram of an exemplary torque curve with shift points foran economy shift schedule;

FIG. 3 is a flow chart of an embodiment for selecting an economy shiftschedule;

FIG. 4 is a flow chart of the embodiment of FIG. 3;

FIG. 5 is a flow chart of the embodiment of FIG. 3; and

FIG. 6 is a flow chart of the embodiment of FIG. 3.

Corresponding reference numerals are used to indicate correspondingparts throughout the several views.

DETAILED DESCRIPTION

The embodiments of the present invention described below are notintended to be exhaustive or to limit the invention to the precise formsdisclosed in the following detailed description. Rather, the embodimentsare chosen and described so that others skilled in the art mayappreciate and understand the principles and practices of the presentinvention.

The present invention relates to an economy-based, transmission shiftschedule which controls the operation of a transmission in a vehicle.With reference to FIG. 1, an exemplary embodiment of a transmissionsetup is provided. A transmission 102 is shown in FIG. 1 with acontroller 104, i.e., transmission control module (“TCM”). Software isdownloaded to the TCM 104 and a wiring harness 106 couples the TCM 104to the transmission 102. A conventional wiring harness 106 includes anouter plastic body that surrounds wires that extend from a TCM connector110 at one end of the wiring harness 106 to a transmission connector 108disposed at the opposite end of the wiring harness 106.

The wiring harness 106 can also include other connectors such as speedsensor connectors. In FIG. 1, for example, an engine or input speedsensor connector 112 couples to an engine or input speed sensor 126 ofthe transmission 102. Likewise, a turbine speed sensor connector 114couples the wiring harness 106 to a turbine speed sensor 128 of thetransmission 102. Also, an output speed sensor connector 116 of thewiring harness 106 couples to an output speed sensor 130 of thetransmission 102. Other possible connectors of the wiring harness 106include a throttle input source connector 120, a throttle positionsensor (TPS) connector 124, a vehicle connector 118 (e.g., VehicleInterface Module (“VIM”) connector), and an alternative transmissionharness mating connector 122. There can be additional connectors and/orharnesses in other embodiments.

As noted, the transmission 102 can include the engine or input speedsensor 126, turbine speed sensor 128, and output speed sensor 130. Thetransmission 102 mounts to an engine (not shown) by coupling a converterhousing 134 of the transmission 102 to a bell housing (not shown) of theengine (not shown). A torque-transferring mechanism 132, e.g., a torqueconverter, of the transmission 102 can include a plurality of lugs 140that couple to a flex plate (not shown) via flex plate bolts (notshown). For purposes of this embodiment, the torque-transferringmechanism 132 will be referred to as a torque converter.

In one embodiment, an internal combustion engine (not shown) can becoupled to the transmission 102 via the torque converter 132. Theinternal combustion engine can be configured to rotatably drive anoutput shaft (not shown) of the engine that is coupled to an input orpump shaft (not shown) of the torque converter 132. The torque converter132 can further include a turbine (not shown) that is coupled viasplines to a turbine shaft (not shown) of the transmission 102. In turn,the turbine shaft (not shown) can be coupled to, or integral with, arotatable input shaft (not shown) of the transmission 102. An outputshaft (not shown) of the transmission 102 can be coupled to or integralwith, and rotatably drives, a propeller shaft (not shown) that iscoupled to a conventional universal joint (not shown). The universaljoint (not shown) can be coupled to, and rotatably drives, a drive axle(not shown) having tires or wheels mounted thereto at each end. Theoutput shaft (not shown) of the transmission 102 drives the tires in aconventional manner via the propeller shaft, universal joint and driveaxle.

In the torque converter 132, a conventional lockup clutch (not shown)can be connected between the pump (not shown) and turbine (not shown) ofthe torque converter 132. The operation of the torque converter 132 isconventional such that it can operate in a so-called “converter” mode or“lockup” mode. The torque converter 132 can operate in “converter” modeduring certain operating conditions such as vehicle launch, low speedand certain gear shifting conditions. In “converter” mode, the lockupclutch (not shown) is disengaged and the pump (not shown) rotates at therotational speed of the engine output shaft (not shown) while theturbine (not shown) is rotatably actuated by the pump (not shown)through a fluid (not shown) interposed between the pump (not shown) andthe turbine (not shown). In this operational mode, torque multiplicationoccurs through the fluid coupling such that the turbine shaft (notshown) is exposed to more drive torque than is being supplied by theengine (not shown), as is known in the art.

The torque converter 132 can operate in “lockup” mode during otheroperating conditions. In the “lockup” mode, the lockup clutch (notshown) is engaged and the pump (not shown) is thereby coupled directlyto the turbine (not shown) so that the engine output shaft (not shown)is directly coupled to the input shaft (not shown) of the transmission102, as is also known in the art.

During operation, as the engine rotatably drives the torque converter132, the engine or input speed sensor 126 detects the rotational speedof the torque converter 132. The torque converter 132 can include ribsor protrusions (not shown) that protrude from the surface of the torqueconverter 132 and which the engine or input speed sensor 126 measuresduring each revolution.

As shown in FIG. 1, the transmission 102 can also include a main case orhousing 136 that encloses a gearbox, i.e., clutch plates and reactionplates, a number of automatically selectable gears, planetary gear sets,hubs, pistons, shafts, and other housings. As previously described, thetransmission 102 can further include a turbine shaft (not shown) whichcan rotate various clutches in the transmission. A gear or tonewheel(not shown) can be coupled to the turbine shaft (not shown) such thatthe turbine speed sensor 128, which couples to the main case or housing136, measures the rotational speed of the gear or tonewheel (not shown).Other transmissions can include alternative ways known to the skilledartisan for measuring turbine speed.

In one embodiment, the transmission 102 can include an output shaft (notshown) which is enclosed by a rear cover 138 of the transmission 102. Tomeasure the output speed of the transmission 102, the output speedsensor 130 can couple to the rear cover 138. A smaller gear or tonewheel(not shown) can be coupled to the output shaft (not shown) such that theoutput shaft and gear or tonewheel rotate together. The output speedsensor 130 is aligned with the gear or tonewheel and measures therotational speed of the output shaft. Thus, over a given period of time,the output speed of the transmission is measured.

Transmission shift schedules and other related instructions are includedin software which is downloaded to the TCM 104. The TCM 104 can controlthe shifting of the transmission by electrically transferringinstructions to the transmission such that certain actions are carriedout by the clutches, pistons, etc. In one non-limiting embodiment, theTCM 104 is part of a transmission control circuit that can furtherinclude an electronic solenoid and valve assembly for controlling theengaging and disengaging of clutch assemblies, etc. Components withinthe transmission 102 can be activated electrically, mechanically,pneumatically, semi-automatically, and/or manually. The transmissioncontrol circuit is able to control the operation of the transmission toachieve desired performance.

Based on instructions in a transmission software program, thetransmission control circuit (e.g., TCM 104) can select a shift scheduledepending on a vehicle's driving condition and execute instructionscontained in the software by sending signals through the wiring harness106 to control the transmission 102. The TCM 104 can also receivemeasurement data from the transmission 102 such as, for example, inputspeed from the input speed sensor 126, turbine speed from the turbinespeed sensor 128, and output speed from the output speed sensor 130. Inan embodiment in which the transmission does not include a torqueconverter 132, the transmission may only have an input speed sensor 126and output speed sensor 130. The TCM 104 can also calculate variousparameters including transmission gear ratio or range, which istypically the ratio of input speed to output speed. In an embodiment inwhich the transmission 102 has a torque converter 132, the transmissiongear ratio or range can also be determined by the ratio of turbine speedto output speed.

The TCM 104 can also receive accelerator pedal position (i.e., throttlepercentage) from a throttle input source, which can be coupled to anengine control module (ECM) for transmitting throttle data over a datalink. Examples of a conventional data link include J1587 data link,J1939 data link, IESCAN data link, GMLAN, Mercedes PT-CAN, Hardwire TPS(throttle position sensor) to TCM, and Hardwire PWM (pulse widthmodulation) to TCM. Information such as accelerator pedal position thatis communicated over the data link is not limited to a particularengine/transmission configuration. Instead, the data link can be adaptedto most vehicle setups.

For background purposes, an economy shift schedule can be selected forimproving the fuel efficiency of a vehicle. The transmission controlcircuit can select the economy shift schedule based on engine andtransmission data. In many setups, the transmission control circuit canoperate according to a downloadable software program or logic whichselects between an economy shift schedule and a performance shiftschedule. The economy shift schedule may be selected, for example, whenthe transmission control circuit detects the vehicle is unloaded or isable to accelerate quickly. To execute the economy shift schedule, forexample, the TCM may command a shift from a higher gear ratio to a lowergear ratio at a lower output speed than if the TCM was commanding thesame shift based on the performance shift schedule. On the other hand,if the TCM detects the vehicle is unable to accelerate quickly and/orpredicts the vehicle is loaded or ascending a steep grade, the TCMselects the performance shift schedule. To implement a performance shiftschedule, for example, the TCM may command a shift from a lower gearratio to a higher gear ratio at a higher output speed than if the TCMwere commanding the same shift based on the economy shift schedule. At ahigher gear ratio, the transmission produces greater torque, forexample, to move a loaded vehicle or assist a vehicle as it ascends asteep grade.

In the present disclosure, aspects of a method of selecting an enhancedeconomy shift schedule are provided. Unlike many conventional economyshift schedules, however, at least one exemplary embodiment of themethod of the present disclosure can be enabled when a vehicle isoperating according to either a performance shift schedule or economyshift schedule. In other words, the aspects of the present disclosureprovide an enhanced, or improved, economy shift schedule which can beselected to provide additional fuel savings to the vehicle. A vehicleoperating according to a conventional economy shift schedule can obtainfurther fuel-saving benefits when predetermined conditions are met forenabling the enhanced or improved economy shift schedule. Alternatively,even if a vehicle is operating according to a performance shiftschedule, the enhanced economy shift schedule can be selected and thetransmission shifting controlled accordingly to achieve improved fuelefficiency. The ability to improve fuel efficiency by selecting theenhanced economy shift schedule when a transmission is operatingaccording to a conventional performance shift schedule is one of manyadvantages of the present disclosure.

In an exemplary aspect, the transmission control circuit can operateaccording to logic for selecting either an economy or performance shiftschedule. Regardless of whether the transmission control circuit selectsthe economy shift schedule or performance shift schedule, further logicenables the transmission control circuit to decide whether to enable athird shift schedule, i.e., the enhanced economy shift schedule asdescribed in the present disclosure. In this aspect, the third shiftschedule (e.g., enhanced economy shift schedule) can only be enabledafter the transmission control circuit selects either the economy shiftschedule or performance shift schedule. As previously described, theenhanced economy shift schedule enables a vehicle to achieve better fuelefficiency than either the economy or performance shift schedule. Inalternative aspects, however, it may be desirable to select the enhancedshift schedule without previously selecting the economy or performanceshift schedule.

In a related aspect of the present disclosure, before the enhancedeconomy shift schedule can be selected, several determinations are madeby the transmission control circuit. Since another advantage of theenhanced economy shift schedule is its implementation into most vehiclesetups (e.g., engine/transmission combinations), the transmissioncontrol circuit learns the engine torque curve at a maximum acceleratorpedal position. This learning can take place at various times, butgenerally takes place when the engine and transmission first begincommunicating with one another (i.e., the first time theengine/transmission combination operates at the maximum acceleratorpedal position). This can vary for different embodiments, and may evenoccur automatically in real-time.

Referring to FIG. 2, an exemplary diagram 200 of an engine torque curve202 is shown as a function of engine speed at a maximum acceleratorpedal position. To learn the engine torque curve, engine torque data canbe communicated to the transmission control circuit (e.g., TCM 104) viaa data link. In this embodiment, the engine torque data is communicatedover the data link when the transmission control circuit is first ableto communicate with a control circuit of the engine. The engine controlcircuit, for example, can have an engine control module thatcommunicates to the TCM 104.

Also shown in FIG. 2 are two shift points 204, 206. To enable or selectthe enhanced economy shift schedule, the transmission control circuitdetermines the current range of the transmission and its correspondinggear ratio. The transmission control circuit also determines, if thetransmission shifts from a lower gear range to a higher gear range, theimpact of engine torque on such a shift. In other words, among manydifferent factors, the transmission control circuit determines whetherthe transmission can complete a shift to a higher gear range withoutexceeding the maximum engine torque in the next range. For purposes ofthis disclosure, the lower gear range has a higher gear ratio than thehigher gear range. In a lower gear range, more output torque istransferred to the rear axle and tires of the vehicle and thus can bepreferable in a performance mode. In a higher gear range, however, therecan be less output torque transferred to the rear axle and tires of thevehicle. Better fuel efficiency can be achieved when a transmissionoperates in a higher gear range.

According to the diagram 200 of FIG. 2, if the transmission is operatingat shift point 204, the transmission control circuit can determine ifshifting to a higher gear range is obtainable. As shown, arrow 208indicates that a shift from shift point 204 to a higher gear range(e.g., shift point 212) can be achieved without exceeding the enginetorque limit of the engine torque curve 202. On the other hand, if thetransmission is operating at shift point 206, the transmission controlcircuit can determine that shifting to a higher gear range (e.g., shiftpoint 214) is not obtainable. Instead, as shown, arrow 210 indicatesthat a shift to the higher gear range cannot be achieved withoutexceeding the engine torque limit of the engine torque curve 202. If thetransmission attempts to shift to the higher gear range from shift point206, the engine will not allow the shift to be completed and vehiclespeed will be reduced. As vehicle speed decreases, the transmissioncontrol module will likely downshift to a lower gear range.

One reason the shift cannot be made from shift point 206 to shift point214 is due to a lack of tractive effort force. Although the shift pointsare shown in FIG. 2 relative to engine torque, in at least oneembodiment the transmission control circuit determines the currenttractive effort force before enabling or selecting the enhanced economyshift schedule. Tractive effort force is the net force acting on thetire patches of the drive wheels which propels the vehicle into motion.During operation, the current tractive effort force can be determined asa function of maximum engine torque, transmission torque ratio, and rearaxle ratio. This will be described in further detail below.

The enhanced economy shift schedule is unlike conventional or nominalshift schedules because it generally operates the engine at a lowerengine speed to reduce the amount of fuel being consumed by the vehicle.Since the enhanced economy shift schedule can be selected when thetransmission is operating according to either a conventional economyshift schedule or performance shift schedule, it is desirable to selectthe enhanced shift schedule when there will be substantially no impacton vehicle productivity. Vehicle productivity, or performance, can referto average vehicle speed. In other words, the enhanced economy shiftschedule can be enabled so long as the average vehicle speed does notsignificantly change. As described above with reference to FIG. 2, ifthe transmission attempts to shift too soon, i.e., such that there is alack of tractive effort force at the wheels, the transmission mayundergo shift cycling. Shift cycling occurs when the transmission shiftsfrom a first gear range to a second gear range and then shifts back tothe first gear range within a relatively short period time. When shiftcycling occurs, vehicle speed changes because the shift from the firstgear range to the second gear range cannot be maintained or held. Thus,two related factors that affect the selection of the enhanced shiftschedule are vehicle productivity and shift cycling.

Note, however, that the weight of the vehicle is not relevant to whetherthe transmission control circuit selects the enhanced economy shiftschedule. Therefore, even if the vehicle is pulling a trailer or otherload, for example, and operating according to a performance shiftschedule, the enhanced economy shift schedule can still be selected solong as vehicle productivity is maintained and the transmission does notundergo subsequent shift cycling.

In addition, it is desirable to enable the enhanced economy shiftschedule as soon as all criteria for doing so are satisfied. Asdescribed above, the enhanced economy shift schedule can also be enabledfor most vehicle setups and therefore it is less dependent on enginemodel, throttle progression, vehicle model, etc.

Referring to FIG. 3, an exemplary embodiment of a method 300 forselecting an enhanced economy shift schedule (ESS) is shown. The method300 includes several steps before enabling or selecting the shiftschedule. In other embodiments, there can be more steps required forenabling or selecting the enhanced economy shift schedule. For instance,in step 302, the transmission control circuit calculates vehicleacceleration. There are several ways vehicle acceleration can bedetermined. First, as shown in FIG. 1, the transmission can include anoutput speed sensor 130 for measuring output speed of the transmission.Vehicle speed information can be communicated to the transmissioncontrol circuit via the data link. Once the transmission output speedand vehicle speed are known, the ratio of the two can be used tocalculate the output acceleration of the transmission (e.g., outputspeed / vehicle speed). Once the output acceleration of the transmissionis known, vehicle acceleration can be calculated based on a ratio of therear axle and tire size. This ratio takes into account losses from thetransmission output shaft to the tire patch.

Vehicle acceleration can also be obtained by taking the derivative ofvehicle speed. As described above, vehicle speed information iscommunicated over the data link to the transmission control circuit. Attimes, this data signal can be slow and therefore the vehicle speedinformation may not be entirely accurate or the most up-to-dateinformation. As such, if vehicle speed information is slowlycommunicated to the transmission control circuit, this can be a lesspreferable means for computing vehicle acceleration.

In step 304, the transmission control circuit determines the position ofthe accelerator pedal in the vehicle. This information can becommunicated to the transmission control circuit via the data link.Accelerator pedal position can have different units, but in oneembodiment, the position is defined as throttle percentage (e.g.,maximum accelerator pedal position equates to 100% throttle and minimumaccelerator pedal position equates to 0% throttle).

In method 300, the current tractive effort force is calculated in step306. As described above, tractive effort force is a function of enginetorque, gear ratio, and torque converter torque ratio. The following isa brief description of how each variable used for calculating tractiveeffort force can be obtained.

The current engine torque can be determined several ways. First, thetorque can be communicated to the transmission control circuit via thedata link. Alternatively, a sensor can be positioned between the engineand transmission for reading engine torque. For example, the sensorcould be positioned on a flywheel or shaft of the engine. As such, thesensor can be electrically coupled to the transmission control circuitto communicate the measured engine torque thereto.

The gear ratio, as described above, is the ratio of input speed tooutput speed. In addition, gear ratio is also the ratio of turbine speedto output speed. The input speed, or engine speed, can be measured bythe input speed sensor 126 as shown in FIG. 1. Similarly, turbine speedand output speed can be measured by the turbine speed sensor 128 andoutput speed sensor 130, respectively.

The torque converter torque ratio is a function of the torque convertermodel and the mode in which the torque converter is operating at thetime of determination. The torque converter model produces a torqueconverter torque ratio, which can be multiplied by the gear ratio toproduce the transmission torque ratio. Above a specified gear range, thetorque converter may be operating in “lockup” mode such that thetransmission torque ratio is unity and is otherwise generally aconventional function of vehicle speed or a predetermined torque ratiovalue. In some embodiments, the transmission torque ratio can alsoinclude an inefficiency factor that models efficiency losses through thegear system and the torque converter of the transmission. In suchembodiments, such gear system/torque converter inefficiencies can bemodelled as a function of gear range and engine speed to produce aninefficiency factor which can be added to, subtracted from or multipliedby the torque ratio, such that the overall torque ratio is generallyreduced by the inefficiency factor. Alternatively or additionally, thegear system/torque converter inefficiencies can be produced in the formof a torque reduction factor that gets subtracted from the tractiveforce.

The transmission control circuit also can calculate or determine therear axle ratio and tire size of the vehicle. The rear axle ratio is aratio of the number of revolutions of the propeller shaft (not shown inFIG. 1) required to turn the rear drive axle (not shown) one completerevolution, and the tire size is the diameter of the tires coupled tothe vehicle. In some embodiments, the rear axle ratio and the tire sizecan be pre-programmed into the transmission control circuit, andaccordingly these parameters are retrieved from the transmission controlcircuit in step 306.

An advantage of the enhanced economy shift schedule over manyconventional shift schedules is the lack of necessity for determiningrolling resistance and aerodynamic forces acting against the vehicle. Asa result, the transmission control circuit has fewer calculations anddeterminations to make before deciding whether to select the enhancedeconomy shift schedule.

Once the variables (e.g., engine torque, gear ratio, torque convertertorque ratio, and rear axle ratio) are calculated, determined, orreceived by the transmission control circuit, the current tractiveeffort force can be computed in step 306. To do so, the current tractiveeffort force, CTEF, is calculated according to the following formula:CTEF=CET*GR*TCTR*RAR, where CET is current engine torque, GR is gearratio, TCTR is torque converter torque ratio, and RAR is rear axleratio. As shown in FIG. 3, once steps 302, 304, and 306 are completed,the method 300 proceeds to B (see FIG. 4).

In FIG. 4, once calculations and values are made and/or received forvehicle acceleration, accelerator pedal position, and current tractiveeffort force, the method 300 for selecting the enhanced economy shiftschedule goes through a number of algorithmic or conditional steps. Forinstance, in step 400, the transmission control circuit compares thecurrent vehicle acceleration to a first threshold or algorithm,Thresh 1. Thresh 1 is generally defined as a constant value or range ofvalues in the enhanced economy shift schedule. The value or range ofvalues for Thresh 1 generally includes low acceleration values, becauseit is desirable to enable the shift schedule only when vehicleproductivity will not be impacted. By setting Thresh 1 as a lowacceleration value or range of values, it is presumed that vehicleproductivity is less impacted when vehicle acceleration is low. In otherwords, if the vehicle acceleration is relatively low, there is anopportunity to shift to a higher gear range and get better fuel mileagewithout disregarding the vehicle operator's intent and negativelyimpacting vehicle productivity. In a non-limiting example, Thresh 1 maybe equal to or less than about 0.5 m/s².

In step 402, the transmission control circuit compares the currentaccelerator pedal position to another threshold value or range, Thresh2. More particularly, in this step, the transmission control circuit isdetermining if there is a change in accelerator pedal position, and ifso, is the change significant enough to not enable or select theenhanced economy shift schedule. Once again, the intent of the vehicleoperator is important. It is presumed that if there is a rapid change inaccelerator pedal position, e.g., from 40% to 90% throttle, the vehicleoperator desires more vehicle speed or output torque (e.g., whenascending a steep grade). In this case, vehicle productivity isnegatively affected if the transmission control circuit enables theenhanced economy shift schedule, and thus the shift schedule cannot beenabled. On the other hand, if the change in accelerator pedal positionsatisfies the condition of step 402, the transmission control circuitwill further evaluate the conditions of steps 400 and 404 beforeenabling the enhanced economy shift schedule. In another non-limitingexample, the condition in step 402 may be satisfied if the change inaccelerator pedal position is less than or equal to about 20% persecond.

In step 404, the transmission control circuit evaluates the currenttractive effort force to a third threshold value, Thresh 3. In thisembodiment, Thresh 3 can have two components. The first component is amaximum tractive effort force for a higher gear range and the secondcomponent is a predetermined constant value or threshold margin value.In this step, the enhanced economy shift schedule can be selected if thecurrent tractive effort force is less than Thresh 3.

As described above, the transmission 102 can have a number, X, ofautomatically selectable gear ranges. Thus, when the transmission isoperating in gear range N, the transmission control circuit determinesthe maximum tractive effort force for gear range N+1. In other words,the transmission control circuit obtains information about the maximumtractive effort force for the next upshift gear range. To do so, thetransmission control circuit receives engine torque data at a fullaccelerator pedal position over the data link. As shown in FIG. 2, theengine torque data is a function of engine speed, which can be measured,for example, by the engine or input speed sensor 126 (FIG. 1). Theengine torque data can be organized to form an engine torque curve 202(FIG. 2).

As an example, the transmission may be currently operating in gear rangeN with shift point 204 (FIG. 2). To enable the enhanced shift schedule,the next higher range gear, N+1, may have a shift point 212. At shiftpoint 212, the transmission control circuit can obtain the maximumengine torque via the torque curve 202. The transmission control circuitcan also determine a maximum tractive effort force at shift point 212 asa function of the maximum engine torque at gear range N+1 (i.e., shiftpoint 212), the gear ratio for gear range N+1, the torque convertertorque ratio for gear range N+1, and the rear axle ratio for gear rangeN+1. Once the maximum tractive effort force for gear range N+1 is known,the comparison in step 404 can be completed.

The second component of Thresh 3 is a predetermined constant value orthreshold margin. As a non-limiting example, the maximum tractive effortforce for gear range N+1 may be determined to be 12,000 Newton. Theenhanced economy shift schedule can set the second component of Thresh 3to be any predetermined value, but for purposes of this example, thethreshold margin may be 1,000 Newton. Thus, the value of Thresh 3 is thetotal of the maximum tractive effort force for gear range N+1 and thethreshold margin, i e, 13,000 Newton. In step 404, if the currenttractive effort force is less than 13,000 Newton, then the condition setforth in step 404 is satisfied.

If, however, the current tractive effort force is greater than 13,000Newton, the shift from gear range N to gear range N+1 cannot becompleted because there is not enough force at the tires. Althoughengine torque is shown in FIG. 2, if the transmission is operating ingear N at shift point 206, an upshift to gear range N+1 (e.g., shiftpoint 214) cannot be achieved without exceeding the maximum enginetorque. Similarly, the same shift cannot be completed if the currenttractive effort force exceeds the total of the maximum tractive effortforce and threshold margin.

In alternative embodiment, the transmission control circuit can selectthe enhanced economy shift schedule and shift the transmission from gearrange N to gear range N+2, where gear range N+1 is skipped or notselected. The same conditions in steps 400, 402, and 404 are evaluatedby the transmission control circuit, and if the conditions aresatisfied, the shift from gear range N to gear range N+2 can beachieved. In this embodiment, the value of Thresh 3 in step 404 includesthe total of the maximum tractive effort force for gear range N+2 andthe threshold margin. In another alternative embodiment, it can bepossible to shift from gear range N to gear range N+3, N+4, . . . N+j,where the transmission has X automatically selectable gear ranges and jis equivalent to X−N, so long as the current tractive effort force isless than the total of the maximum tractive effort force for gear rangeN+j and the threshold margin.

In one aspect of this alternative embodiment, step 308 can be anoptional step. In other words, step 308 can either be included in method300 if skip shifts are desirable, or method 300 can be configured suchthat step 308 is not an active step. In one aspect, step 308 can beenabled or disabled by a user. In a different aspect, step 308 may notbe included in method 300 (and thus skip shifts according to method 300are not possible). In step 308, the transmission control circuit candetermine the maximum tractive effort force for each selectable upshiftgear range (e.g., N+1, N+2, . . . , N+J, where J=X−N). Thus, for thosetransmissions which may have tight gear steps, the transmission controlcircuit can determine if the transmission can shift from gear range N toan upshift gear range on the basis of the maximum tractive effort forcefor each upshift gear range. If one or more upshift gear ranges can beskipped, the transmission control circuit can control the shift fromgear range N to gear range N+M, where M is an integer between 1 and J.

As a non-limiting example, a 10-speed transmission can have 10 forwardranges (i.e., X=10). Method 300 can proceed through steps 302, 304, and306 as previously described. If step 308 is performed, the transmissioncontrol circuit can determine the maximum tractive effort force for eachupshift gear range between gear range N+1 and N+J. Suppose thetransmission is operating in a second range (i.e., N=2 and J=8), thepossible upshift ranges therefore would be ranges 3-10. If step 308 isnot performed, then the transmission control circuit would be comparingthe current tractive effort force in second range (N=2) to the maximumtractive effort force in third range (i.e., N+1). If, however, step 308is performed, the transmission control circuit can determine the maximumtractive effort force for third range (N+1), fourth range (N+2), fifthrange (N+3), . . . , and tenth range (N+J). After this determination,the transmission control circuit proceeds to performing steps 400 and402. Assuming those conditions are met, the transmission control circuitcan then perform step 404.

In step 404, the threshold value, Thresh 3, can comprise a set of one ormore values depending on the number of selectable upshift gear ranges.In the event step 308 is performed, Thresh 3 can include maximumtractive effort force values for all upshift gear ranges plus an addedconstant value (e.g., a threshold or margin). In this embodiment, thetransmission control circuit performs a plurality of comparisondeterminations in step 404. For example, the current tractive effortforce can be compared to the maximum tractive effort force for eachupshift gear range, and whichever highest upshift range has a maximumtractive effort force that is greater than the current tractive effortforce is the gear range to which the transmission control circuit willshift to in step 500. In the previous example, if the transmission is insecond range, and the transmission control circuit determines that thecurrent tractive effort force in second range is less than the maximumtractive effort force in third range and fourth range, but not fifthrange and above, the transmission control circuit can then upshift tofourth range and skip third range.

Alternatively, method 300 can be defined such only a limited number ofgear ranges can be skipped. This can be predetermined before method 300is loaded into the transmission control circuit, or a user may have thecapability to set the number of allowable skip shifts. In either case,the transmission control circuit may determine that a higher gear rangeis obtainable (e.g., the net tractive effort force is less than themaximum tractive effort force for that higher gear range), but method300 may limit the transmission control circuit from shifting to thehigher gear range because doing so would exceed the limit set for thenumber of gear ranges that can be skipped. Since method 300, however, iscontinuously performed, the transmission may shift from second range tofourth range in a first iteration and then shift from fourth range tosixth range in a second iteration, assuming the conditions set forth inmethod 300 are continuously met. This, of course, assumes too thatmethod 300 limits the controlled shifting to only skip one gear range(e.g., second gear range to fourth gear range, skipping third gearrange).

As shown in FIG. 4, if any one of the conditions set forth in steps 400,402, or 404 cannot be satisfied, the enhanced economy shift schedule isnot enabled or selected and method 300 repeats steps 302, 304, and 306.However, once the conditions set forth in steps 400, 402, and 404 aresatisfied, the enhanced economy shift schedule can be enabled orselected in step 406. At least in this embodiment, this completes theconditional limitations for enabling or selecting the enhanced economyshift schedule. Once the shift schedule has been selected, method 300proceeds to step 500.

Referring to the embodiment of FIG. 5, once the enhanced economy shiftschedule is enabled or selected, the transmission control circuit cancontrol transmission shifting to achieve better vehicle fuel economy. Todo so, in step 500, the transmission control circuit can shift to ahigher gear range having a lower gear ratio. Once the shift to thehigher gear range is complete, the transmission control circuit canactivate a waiting period, t_(Delay), in step 502. Alternatively, step502 can be optional in some embodiments.

In step 504, the transmission control circuit determines if thetransmission undergoes shift cycling after the enhanced economy shiftschedule is selected. Again, in one embodiment, step 504 is performedafter the waiting period expires in step 502. In a different embodiment,however, step 504 can be performed immediately after step 500. Thetransmission control circuit can repeatedly perform step 504 to ensurethe transmission does not undergo shift cycling. As described above,shift cycling can be disadvantageous to selecting the enhanced economyshift schedule because vehicle productivity can be negatively affected.For example, if the transmission downshifts from the higher gear range(which it shifted to in step 500) to the lower gear range, the averagevehicle speed may decrease thereby affecting vehicle productivity.

There can be different results if the transmission undergoes shiftcycling. In one aspect, after the transmission control circuitdetermines the transmission shifted to a lower gear range (i.e., highergear ratio), method 300 continues to step 600 (FIG. 6). In step 600, thetransmission control circuit can activate a counter variable. Thecounter variable can be initially set at a value of zero by the enhancedeconomy shift schedule. However, in step 600, the counter variable isincreased by an increment of one. Each time the transmission does ashift cycle from a lower gear ratio to a higher gear ratio, the value ofthe counter variable can be increased.

In step 602, the condition of the counter variable is tested. In thisembodiment, when the counter variable exceeds two, i.e., thetransmission downshifts from a lower gear ratio to a higher gear ratiomore than two times, the condition in step 602 is satisfied and method300 proceeds to step 604. If the condition is not met in step 602, thetransmission control circuit can reselect the higher gear range (e.g.,lower gear ratio) automatically (this step is not shown in FIG. 6) or itcan repeat steps 302, 304, and 306 at the lower gear range. In thelatter condition, the enhanced economy shift schedule is disabled untilthe conditions set forth in steps 400, 402, and 404 are satisfied.

If, however, the counter variable does satisfy the condition in step602, method 300 continues to step 604 where the threshold value, Thresh3, is reevaluated and/or adjusted. In step 604, for example, theconstant value or threshold margin can be adjusted to prevent furthershift cycling. In the previous example, the threshold margin was set at1,000 Newton. If shift cycling is detected by the transmission controlcircuit, the threshold margin can be adjusted by 500 Newton, forexample, to allow the transmission to operate in the enhanced economyshift schedule. If the transmission can continually operate in theenhanced economy shift schedule at the adjusted threshold margin withoutshift cycling, the transmission control circuit repeats method 300 todetermine if the next higher gear range can be selected to furtherreduce engine speed and improve fuel savings. If, however, thetransmission control circuit detects further shift cycling at thereduced threshold margin, the threshold margin can be further adjustedby 250 Newton, for example. Step 604 can be continuously performed untilthe threshold margin approaches 0 Newton and the current tractive effortforce no longer is less than the maximum tractive effort force for thenext higher gear range.

As shown in FIG. 6, after step 604 is completed, method 300 continues tostep 606 in which the counter variable is reset. Step 606 can beoptional, but in this embodiment it allows the transmission to downshiftto a higher gear ratio at least twice (after Thresh 3 has been adjusted)before the transmission control circuit intervenes and determineswhether to disable or deselect the enhanced economy shift schedule.

As described above, the transmission control module continuouslyperforms method 300 regardless of whether the enhanced economy shiftschedule has been selected. For instance, if the shift schedule has beenselected and the transmission control circuit is controlling shiftsaccording to the shift schedule, the control circuit continuouslyperforms each step to further reduce engine speed and improve fuelefficiency until at least one of the conditions set forth in method 300cannot be satisfied. Therefore, for a transmission having Nautomatically selectable gear ranges, the transmission control modulecan control an upshift from gear range N to gear range N+1. Once theshift to gear range N+1 is complete, the transmission control circuitwill determine if the transmission can hold or maintain the gear range,and if so, the control circuit will perform method 300 again anddetermine if the transmission can shift to gear range N+2.

In one aspect of the present disclosure, once the enhanced economy shiftschedule is selected, the conditions for disabling or deselecting theshift schedule can be made difficult to satisfy. This is particularlytrue if vehicle productivity is maintained and the transmission controlcircuit does not detect shift cycling. There are, however, severalconditions that can cause the transmission control circuit to disable ordeselect the enhanced economy shift schedule.

In one instance, the enhanced economy shift schedule can be disabledwhen there is a sudden drastic change in accelerator pedal position. Asdescribed above, the accelerator pedal position, or throttle percentage,is data that is transferred between the engine control circuit and thetransmission control circuit via the data link. In other embodiments,there may be other means for receiving or determining accelerator pedalposition. Although not shown in method 300, while the transmissionoperates according to the enhanced economy shift schedule, thetransmission control circuit continuously monitors accelerator pedalposition and compares it a threshold value (i.e., this is a differentstep and threshold value than described above relative to step 402). Inthis instance, the transmission control circuit is monitoring the changein accelerator pedal position. There can be a lag filter in place suchthat as accelerator pedal position is communicated to the transmissioncontrol circuit via the data link, a slow or moderate increase or changein accelerator pedal position will not trigger an alert or signal to thecontrol circuit. In other words, the value of the current acceleratorpedal position can be heavily filtered so that, unless the change inaccelerator pedal position is sudden and drastic, the transmissioncontrol circuit will not disable the enhanced economy shift schedule.

If, for example, the accelerator pedal position changes from 10%throttle to 70% throttle in a short amount of time, the transmissioncontrol circuit may disable the shift schedule to enable thetransmission performance to meet the intended desire of the vehicleoperator. For practical purposes, a vehicle operator can ease into theaccelerator pedal without the transmission control circuit disabling theenhanced economy shift schedule. Note, however, that if the vehicleoperator eases off the accelerator pedal causing a decreasing change inaccelerator pedal position, the transmission control circuit may notdisable or deselect the shift schedule even if the change is suddenand/or drastic.

In another instance, the transmission control circuit may disable ordeselect the enhanced economy shift schedule when the accelerator pedalis at a maximum position (e.g., 100% throttle) and vehicle accelerationis below a threshold value. In this instance, the vehicle may beascending a steep grade pulling a heavy load. The accelerator pedal maybe at its maximum position, but the vehicle may not be accelerating upthe incline due to the steep grade and the vehicle's weight. Thus, thetransmission control circuit will disable or deselect the enhancedeconomy shift mode and select a performance shift schedule, for example,to provide additional torque to ascend the steep grade.

If the transmission control circuit detects shift cycling, the enhancedeconomy shift schedule may be disabled or deselected. As describedabove, shift cycling can negatively impact vehicle productivity andtherefore this is another condition in which the transmission controlcircuit can disable or deselect the enhanced economy shift schedule.

In another aspect, the transmission control circuit can disable ordeselect the enhanced economy shift schedule if the required tractiveeffort force is substantially close to the maximum obtainable tractiveeffort force for the current gear range. In this condition, the amountof force at the tires of the vehicle is at or near the maximum amount offorce obtainable at the tires in the current gear range. In other words,if the transmission control circuit determines that the requiredtractive effort is near the current maximum obtainable tractive effortforce, the enhanced economy shift schedule will be disabled ordeselected because the control circuit determines the grade or loadcannot be held (i.e., failure to disable the enhanced economy shiftschedule may result in a loss of vehicle speed and/or a downshift to alower gear range).

Torsional limitations can also be incorporated into the enhanced economyshift schedule. These limitations can prevent the transmission controlcircuit from enabling or selecting the shift schedule, or when the shiftschedule has already been selected, these limitations can cause theshift schedule to be deselected or exited therefrom. The torsionallimitations, as shown in FIG. 2, can be instructions or rules forshifting from a lower gear range to a higher gear range that cannot beviolated. In many instances, the torsional limitations are in place toprotect the structural integrity of the transmission and its workingparts.

While exemplary embodiments incorporating the principles of the presentinvention have been disclosed hereinabove, the present invention is notlimited to the disclosed embodiments. Instead, this application isintended to cover any variations, uses, or adaptations of the inventionusing its general principles. Further, this application is intended tocover such departures from the present disclosure as come within knownor customary practice in the art to which this invention pertains andwhich fall within the limits of the appended claims.

1. A method of selecting an economy mode shift schedule for shifting atransmission between a plurality of selectable gear ranges, thetransmission being coupled to a powered vehicle and having atransmission control circuit, and the vehicle having an input controlcircuit for controlling a powered input, comprising: calculating vehicleacceleration and determining a change in accelerator pedal position;determining a net tractive effort force of the vehicle for a currentgear range of the transmission; comparing the net tractive effort forcefor the current gear range to a maximum tractive effort force for adesired gear range; selecting the economy mode shift schedule for thetransmission based on the comparison; and controlling shifting betweenone or more gear ranges of the transmission according to the economymode shift schedule.
 2. The method of claim 1, further comprisingcomparing the vehicle acceleration to a threshold.
 3. The method ofclaim 2, wherein if the vehicle acceleration exceeds the threshold, theselecting and controlling steps are not performed.
 4. The method ofclaim 1, further comprising comparing the change in accelerator pedalposition to a threshold.
 5. The method of claim 4, wherein if the changein accelerator position exceeds the threshold, the selecting andcontrolling steps are not performed.
 6. The method of claim 1, whereinif the net tractive effort force is less than the total of the maximumtractive effort force and a threshold, the selecting and controllingsteps are completed.
 7. The method of claim 6, wherein if the nettractive effort force is less than the total of the maximum tractiveeffort force and the threshold, the transmission shifts from a lowergear range to a higher gear range.
 8. The method of claim 7, furthercomprising determining if, after the transmission shifts from the lowergear range to the higher gear range, the transmission shifts from thehigher gear range to the lower gear range within a period of time. 9.The method of claim 8, further comprising adjusting the threshold if thetransmission shifts from the higher gear range to the lower gear rangewithin the period of time.
 10. The method of claim 1, wherein thedetermining the net tractive effort force comprises: receiving inputtorque data corresponding to input speed and a maximum accelerator pedalposition; computing a ratio value of a rear axle and tire size of thevehicle; determining a state of a torque-generating mechanism of thetransmission; determining gear ratios for the plurality of selectablegear ranges of the transmission; and computing the net tractive effortforce of the vehicle as a function of the input torque data, the ratiovalue of the rear axle and tire size of the vehicle, the state of thetorque-generating mechanism, and the gear ratios of the transmission.11. The method of claim 10, further comprising determining vehicle speedand transmission output speed, wherein the computed ratio value is afunction of vehicle speed and transmission output speed.
 12. The methodof claim 10, wherein the determining a state of a torque-generatingmechanism comprises determining if a torque converter of thetransmission is in a converter mode or lockup mode.
 13. The method ofclaim 10, wherein the receiving input torque data comprises receivinginput torque data over a data link established between the transmissioncontrol circuit and the input control circuit.
 14. The method of claim10, wherein the receiving input torque data comprises measuring inputtorque with a sensor disposed between the input and transmission. 15.The method of claim 1, further comprising detecting shift cycling. 16.The method of claim 1, wherein after the selecting step, the calculatingstep, determining step, and comparing step are continuously performed.17. The method of claim 16, further comprising deselecting the economymode shift schedule if the change in accelerator pedal positionincreases beyond a threshold.
 18. The method of claim 17, wherein thethreshold comprises a filtered value of accelerator pedal position. 19.The method of claim 16, further comprising: comparing the calculatedvehicle acceleration to a first threshold and the change in acceleratorpedal position to a second threshold; and deselecting the economy modeshift schedule if either the calculated vehicle acceleration exceeds thefirst threshold or the change in acceleration pedal position exceeds thesecond threshold.
 20. The method of claim 1, further comprising:detecting a change in vehicle speed; and deselecting the economy modeshift schedule if the detected change exceeds a threshold.
 21. A systemfor selecting an economy mode shift schedule for a motor vehicle,comprising: a transmission having a torque converter and a plurality ofselectable gear ranges; a transmission control circuit including acontrol module having the economy mode shift schedule stored therein,the transmission control circuit configured to operably control thetransmission; an engine control circuit configured to control operationof an engine, the engine being operably coupled to the transmission; acommunication link configured to transfer information between thetransmission control circuit and the engine control circuit; wherein,the control module further includes instructions stored therein forexecutably controlling the transmission control circuit to receiveengine torque data from the communication link, calculate vehicleacceleration, determine an accelerator pedal position, determine a modeof the torque converter, compute a net tractive effort force of thevehicle, compare the vehicle acceleration to a first threshold, theaccelerator pedal to a second threshold, and the net tractive effortforce to a third threshold, select the economy mode shift schedule forthe transmission based on the comparison; and control shifting betweengear ranges of the transmission according to the economy mode shiftschedule.
 22. The system of claim 21, wherein the instructions stored inthe control module include instructions that are executable by thetransmission control circuit to determine the net tractive effort forceas a function of the engine torque data, the gear ratio of a selectedgear range, and the mode of the torque converter.
 23. The system ofclaim 22, wherein the instructions stored in the control module furtherinclude instructions executable by the transmission control circuit tocompute a ratio value of a rear axle and tire size of the vehicle anddetermine gear ratios for the selectable gear ranges of thetransmission.
 24. The system of claim 21, wherein the instructionsstored in the control module further include instructions executable bythe transmission control circuit for controlling a shift from a firstgear range to a second gear range.
 25. The system of claim 24, whereinthe instructions stored in the control module further includeinstructions executable by the transmission control circuit to determineif, after the transmission shifts from the first gear range to thesecond gear range, the transmission shifts from the second gear range tothe first gear range within a period of time.
 26. The system of claim21, wherein the third threshold comprises a maximum tractive effortforce and a tractive effort threshold value.
 27. The system of claim 26,wherein the instructions stored in the control module further includeinstructions executable by the transmission control circuit foradjusting the tractive effort threshold value.
 28. A method of operatinga motor vehicle at an optimal vehicle speed without negatively affectingvehicle productivity, the vehicle having an engine coupled to atransmission, comprising: (a) determining gear ratios of all gear rangesof the transmission; (b) receiving engine torque data as a function ofengine speed for all gear ranges; (c) calculating vehicle accelerationand determining accelerator pedal position; (d) determining a nettractive effort force of the vehicle for a current gear range of thetransmission; (e) comparing the vehicle acceleration to a firstthreshold, the accelerator pedal position to a second threshold, and thenet tractive effort force to a third threshold; (f) selecting an economymode shift schedule for the transmission based on the comparison; and(g) controlling shifting between one or more gear ranges of thetransmission according to the economy mode shift schedule.
 29. Themethod of claim 28, wherein the controlling shifting comprisesdetermining if an upshift from a lower gear range to a higher gear rangecan be completed.
 30. The method of claim 29, further comprisingdetermining if, after the upshift from a lower gear range to a highergear range is completed, the transmission downshifts from the higherrange to the lower range within a period of time.
 31. The method ofclaim 30, further comprising adjusting the third threshold when thetransmission downshifts from the higher range to the lower range withinthe period of time.
 32. The method of claim 28, wherein, when theeconomy mode shift schedule includes at least a first gear range havinga first gear ratio, a second gear range having a second gear ratio, anda third gear range having a third gear ratio, the second gear ratiobeing less than the first gear ratio and the third gear ratio being lessthan the second gear ratio, the controlling shifting comprises shiftingfrom the first gear range to the second gear range.
 33. The method ofclaim 32, wherein, after the shifting from the first gear range to thesecond gear range, repeating steps (a)-(g).
 34. The method of claim 33,further comprising shifting from the second gear range to the third gearrange.
 35. The method of claim 32, wherein the controlling shiftingcomprises shifting from the first gear range to the third gear range.36. A method of selecting an economy mode shift schedule for atransmission having X selectable gear ranges and coupled to a poweredvehicle, the transmission having a transmission control circuit and thevehicle having an engine control circuit for controlling an engine,comprising: calculating vehicle acceleration and a change in acceleratorpedal position; computing a net tractive effort force of the vehicle fora current gear range N of the transmission, where N<X; determining amaximum tractive effort force for all upshift gear ranges, the upshiftgear ranges comprising gear ranges N+1, N+2, . . . , and N+J, whereJ=X−N; comparing the net tractive effort force to each maximum tractiveeffort force; and selecting the economy mode shift schedule for thetransmission based on the comparison.
 37. The method of claim 36,further comprising controlling shifting between gear range N and one ofthe upshift gear ranges.
 38. The method of claim 37, further comprising:(a) determining which of the upshift gear ranges has a maximum tractiveeffort force greater than the net tractive effort force; (b) for thoseupshift gear ranges satisfying the condition of step (a), calculatingthe difference between the maximum tractive effort force of thoseupshift gear ranges and the net tractive effort force; and (c)identifying the upshift gear range corresponding to the smallestdifference calculated in step (b).
 39. The method of claim 38, whereinthe controlling step comprises shifting from gear range N to the upshiftgear range identified in step (c).
 40. The method of claim 39, furthercomprising determining if, after the shift from gear range N to theupshift gear range, the transmission downshifts from the upshift gearrange to gear range N within a period of time.
 41. The method of claim40, further comprising adjusting the maximum tractive effort forceassociated with the upshift gear range when the transmission downshiftsfrom the upshift gear range to gear range N within the period of time.42. The method of claim 38, wherein the controlling step comprisesshifting from gear range N to upshift gear range L, where L is between Nand M, and upshift gear range M corresponds to the upshift gear rangeidentified in step (c).
 43. The method of claim 36, further comprisingadding a constant threshold value to each maximum tractive effort force.